Owing to the feature sizes of less than 0.3 μm that can be realized in modern metal oxide semiconductor (MOS) circuit technology, it has become possible to realize transceivers for signal frequencies in the GHz range. As wireless communication continues to advance into all areas of everyday life, the demand for ever higher data transmission rates is rising at the same time. Since the frequency bands in the lower GHz range that can be utilized for free wireless communication are restricted, in the future higher modulation methods will be used with the aim of transmitting higher data rates despite this restriction. The intention is not to have to increase the available channel bandwidths in this case. For some analog function groups in the transceivers, higher modulation methods such as 4QPSK or quadrature phase shift keying, require new circuitry solutions enabling linear or at least more linear signal processing. In this case, the intention is at least to maintain the hitherto achieved properties of such circuits and the advantages thereof. Moreover, compatibility with the currently existing mobile radio standards based for example on GFSK or Gaussian frequency shift keying is intended to be possible.
It is desirable, therefore, for fundamental electrical properties in MOS circuits, such as current consumption, dynamic range, gain or transition frequency, to be kept substantially constant over the technically relevant temperature range from approximately −40° to +140°. It is an aim here to keep constant not just respectively one of the characteristic quantities of integrated circuits, but rather all of said characteristic quantities concurrently over the temperature range.
In principle, MOS circuits for analog linear signal processing are known as such. By way of example, the document M. Gräfe, J. Oehm, K. Schumacher: “A Wide Range dB-Linear Variable Gain CMOS Amplifier”, Proceedings ESSCIRC '97, September 1997, specifies a so-called square law circuit which can process analog voltage signals in linear fashion.
However, circuits of this type have the property that circuit characteristic quantities such as current consumption, dynamic range, gain and transition frequency cannot all be kept constant simultaneously over the technically relevant temperature range, rather temperature independence can be achieved in each case only for some of these characteristic quantities.
The constancy of the transconductance of a transistor amplifier, for example, can be improved by the current through the transistor being temperature-controlled. Over the relevant temperature range mentioned, however, it is necessary for the current to be approximately doubled in order still to be able to ensure constant conditions particularly at high temperatures. These high current consumptions are undesirable, however.